Pellet impact drill bit with controlled pellet return



1957 J. E. ORTLOFF PELLET IMPACT DRILL BIT WITH CONTROLLED PELLET RETURN Filed April 9, 1954 2 Sheets-Sheet l 3 2 =IJ Mm Inventor John E. Offloff By Atforney Jan. 29, 1957 J, E, ORTLOFF PELLET IMPACT DRILL BIT WITH CONTROLLED PELLET RETURN Filed April 9. 1954 2 Sheets-Sheet 2 FIG."II

FIG-8 John E. Orfloff Inventor By Q/KJ/ Attorney United States Patent PELLET IMPACT DRILL BIT WITH CONTROLLED PELLET RETURN Application April 9, 1954, Serial No. 422,127

4 Claims. (Cl. 255-61) The present invention is directed to an improvement in a novel type of apparatus for drilling bore holes in the earth by a process known as pellet impact drilling. This invention is particularly concerned with :an improved means for controlling the efficiency of recycling of pellets into the drilling apparatus.

The basic principles of the pellet impact technique for the drilling of bore holes in the earth involve the use of a stream of fluid pumped from the surface of the earth through a tubular member to a jet nozzle adapted to provide a high velocity jet of fluid directed downwardly toward the bottom of the bore hole. Means are provided to entrain in the high velocity fluid jet a multitude of hard, dense pellets which are accelerated to high velocity in the jet stream and thereby acquire considerable kinetic energy so that when the pellets impinge against the formation the resulting impact and fracturing forces exert a drilling action. pellets from the up-flowing returning stream of fluid and reintroducing the pellets into the jet stream. Preferably the pellets that are employed are smooth, non-abrasive, essentially spherical, and of substantial size, in the range of about one-eighth inch to about one inch in diameter. The basic principles of the technique of drilling by pellet impact are set forth in co-pending application Serial No. 268,873, filed by Philip S. Williams on January 29, 1952, and entitled Pellet Impact Method and Apparatus.

One of the limiting factors in the efliciency of drilling by the pellet impact technique is the rate at which pellets can be recycled into the zone where they are entrained in the fluid jet. hi the co-pending Williams application referred to, one disclosed method for eliecting the recycling of pellets involves the use of a combination of a primary nozzle and a secondary nozzle, or mixing chamber, having a configuration such that the bore hole annulus above the secondary nozzle is enlarged to provide a gravity settling zone where the tip-flowing fluid velocity is markedly decreased. This decrease in velocity causes the pellets to separate from the circulating fluid so that they can be drawn into the secondary nozzle by a combination of gravity action and of fluid flow into the secondary nozzle, the latter action being brought about, at least in part, by the aspirating effect resulting from the passage of the fluid jet from the primary nozzle into the secondary nozzle. Experimental studies indicate that other factors, such as a random vortex action of the fluid in the vicinity of the point of entry into the secondary nozzle, also contribute to pellet recycling.

Observations of pellet action with a primary and sec-- ondary nozzle arrangement of the type described indicate that the recycled pellets become segregated roughly into two groups in the borehole annulus in the vicinity of the inlet to the secondary nozzle, one group forming a more or less stationary cloud of pellets suspended in the fluid above the secondary nozzle opening and the other group forming a circulating stream of pellets below the stationary cloud referred to. The undulating interface be tween the two pellet groups can serve as a deflector that Means are also provided for separating r 2,779,571 Patented Jan. 29, 1957 directs the circulating group into the secondary nozzle entrance. However, if the interface is a considerable dis tance above the secondary nozzle entrance the pellet recycling action is ineflicient, whereas if the interface is too close to the secondary nozzle entrance the stationary portion of pellets presents a barrier to the circulating pellets. Variations in hole gage, fluid flow rate, and other drilling factors make the control of the position of the interface and resultant eflicient pellet recycling quite diificult.

It is one object of the present invention to provide means for improving the efliciency of re-entry of pellets into the secondary nozzle or mixing chamber of a pellet impact bit.

In accordance with this invention one side of the secondary nozzle entrance is blocked off from the up-flowing stream of recycle fluid so as to cause the fluid to pass by the entry to the secondary nozzle to a low velocity zone above the secondary nozzle Where it is free to reverse its direction completely and flow into the top of the secondary nozzle. The pellets carried by the upflowing recycle stream will follow the reversing fluid direction and will enter the secondary nozzle at a fixed and efl lcient rate.

The nature and objects of the invention will be more fully understood when reference is made to the accompanying drawing in which:

Figure 1 is a sectional elevation of one embodiment of the invention in drilling position in a bore hole in the earth;

Figure 2 is a section taken on line 11-11 of Figure 1;

Figure 3 is a section taken on line Illlll of Figure 1;

Figure 4 is a section taken on line IV-lV of Figure 1;

Figure 5 is a section taken on line V-V of Figure l;

Figure 6 is a section taken on line VI-VI of Figure 1;

Figure 7 is a section taken, on line VlL-VII of Figure 1;

, Figure 8 is a sectional elevation of a second embodiment of the invention shown in drilling position in a bore hole;

Figure 9 is a broken elevation taken in the direction IXIX of Figure 8;

Figure 10 is a section taken on line X-X of Figure 8;

Figure 11 is a section taken on line XL-Xl of Fig ure 8;

Figure 12 is a section taken on line XII-Jill of Figure 8;

Figure 13 is a section taken on line Xlll-XIll of Figure 8 Figure 14 is a section taken on line XlV--XIV of Figure 8.

Referring now to Figures 1 to 7, inclusive, a bore hole 10 is shown in which is positioned a drilling apparatus that embodies the present invention. The apparatus is supported in the bore hole on a tubular support member 12 which is adapted for attachment to the lower end of a drill pipe by means not shown. The lower end of member 12 terminates in a primary nozzle element 13. Surrounding support member 12 and defining therewith an annular space 22 is an elongated essentially cylindrical member 14 which may be termed a pellet recycle sleeve. Fitted within the upper end of sleeve 14 is a deflector member 15 which fills a portion of the annular space 22 and also serves as a connecting member between the top of sleeve 14 and the support member 12. The lower end of sleeve 14 is provided with a foot or shroud 16 of essentially frusto-conical configuration so that the drilling apparatus may rest on the reduced diameter portion of the bore hole.

Supported within the sleeve 14 and positioned below primary nozzle 13 is an open ended tubular member or secondary nozzle 17 that is placed in substantial alignment with the primary nozzle 13. A plug member 18 u fixed within and attached to the recycle sleeve 14 serves as a supporting element for the top of the secondary nozzlc. Plug member 18 has a tapered throat 19 the lower end of which communicates with the top of the scout" airy ndzzlt: and the upper end of which encloses the prii. nozzle while providing a pellet r'e-entry opening Fret"- erably the secondary nozzle is slightly inclined as shown and sleeve 14 is provided at its lower end with a side opening it) to permit pellets that leave the secondary nozzle to be directed toward one side of the bore hole so that when the apparatus is rotated by the drill string the pellets may be caused to sweep the full diameter of the hole.

A pair of partition battles 21 are positioned within the annular space between secondary nozzle 1'! and sleeve 14 over the entire length of the secondary Boil lit; and extend into the lower portion of the annular space 22 between member 12 and sleeve 14. Theupper and lower terminations of the partitions 2?. are shown by the phantom lines in Figure l.

in order that there may be proper division between the primary circulated fluid, that is the volume of fluid that flows down through the drill pipe, through the apparatus and heel; up the bore hole in the annulus between the drill pipe and the bore hole, and the recycled fluid, that is the quantity of fluid that reenters the top of the sec ondary nozzle, a plurality of horizontal slots 26 are pro vided in the wall of the recycle sleeve l4 somewhere in the vicinity of the top of the partition oafiics 21. The number and size of slots 26 required may be varied for proper operation depending on such parameters as pri mary fluid flow, nozzle diameters, etc. Again depending on fluid flow requirements, a plurality of vertical fluid flow ports 23 may or may not be required in the deflector member 15.

In utilizing the apparatus illustrated in Figure l drilling is conducted much in the same manner as described in the aforementioned Williams application. ..luid is pumped down through the drill pipe into tubular member 12 and leaves the nozzle 13 in the form of a high velocity stream which passes through the throat l9 and enters the secondary nozzle 17 where it combines with additional fluid that has been aspirated into the throat 19 from the annular space 22. The combined primary and recycled fluid streams pass through the secondary nozzle to impinge on the bottom of the bore hole. The circulating fluid returns up through the space etween sleeve ltd and nozzle 17 and carries with it pellets 3% that have been placed in the bottom of the bore hole. A portion of the upflowing fluid roughly equivalent to the quantity of fluid being pumped down the drill string passes into the bore hole annulus through the slots 26 and the slots 23. The recycled fluid and the pellets continue on up one side of the annular space 22 and are deflected to the other side of the annular space by the deflector l and by downward flowing fluid that is being aspirated into the throat 19. The partition bafi'ies 21 prevent the recycled fluid and pellets from entering the throat 1) until they have reached a point some distance above the entrance to the throat. Thus the pellets will be recycled into the secondary nozzle in a more orderly fashion than results with the simpler primary and secondary nozzle arrangement disclosed in the aforementioned co-pending application.

For most eflhci'ent recycling of pellets it is preferred that a pellet opening or side door 27 be provided in the side of sleeve 14 in a region intermediate the ends of the secondary nozzle as shown. This side door has been found to prevent the jamming of pellets in the upper portion of the space between sleeve 14 and nozzle 17 as it permits some of the pellets to leave the apparatus and travel up the bore hole annulus to a region above the top of the defiectormemb'er l5 where the upward fluid velocity suddenly decreases because of the enlarged annulus in that region. The pellets that are recycled in this manner will also enter the top of the annulus 22 "on the side I opposite the deflector 15 and will be recycled in the manner shown. The latter recycling is also aided by the fact that the top of the deflector 15 has a downward inward slope. When the side opening 27 is used some of the primary and recycling fluid will also leave the apparatus and flow into the bore hole annulus through that opening. Thus when opening 27 is used the slots 23 and 26 will be desi ned to permit the outflow at less fluid than when the opening 27 is not used. The optimum position for opening 27 appears to be at that point where the clean ance between sleeve 14 and nozzle 17 becomes less than two pellet diameters.

A simplified embodiment of the invention employing the same principle of battling is shown in Figures 8 to 14,

' inclusive. This apparatus is shown in Figure 8 as a sectional elevation in position in a bore hole 10. A cylindrical St port member 32 similar to member 12 of Figure l is provided. This member is likewise attachable to the lower end of a drill string and terminates at its lower end in a primary nozzle 33. Attached to each side of member 32 and extending a considerable distance below that member two elongated plates 34 that are arranged in essentially parallel relation. Each of the plates terminates at its lower end in a foot portion 35 that is essentially shaped in the form of a portion of a frustum of a cone, i. e. an essentially semi-circular section of a shroud of the type of member to in Figure l.

Positioned between the plates 34 and supported thereby is a secondary nozzle member 37 which is essentially an open-ended tube, a portion of the top and one side of which has been cut away. The unremoved portion of the top of member 3'7 is fastened to the lower end of member 32 so that the primary nozzle 33 is directed into the secondary nozzle while leaving opening for pellets to enter the secondary nozzle alongside of the primary nozzle. Preferably, as in the case of the embodiment of Figure l, the secondary nozzle is slightly inclined as shown, and the lower portion of the secondary nozzle that would normally extend out beyond the apparatus has been cut off on the bias, making an opening dd.

7 A pair of partition haflles 35 are attached to member 32 at right angles to the plate 34 and to the reduced diameter portion of support member 32 so that pellets travelling up the bore hole annulus on the side opposite from the opening in the top of the secondary nozzle will be prevented from entering the secondary nozzle until they have travelled to a region above the top of plates 34-. These partition battles extend down to a region ad jacent the secondary nozzle opening as shown in Figure 9.

The operation of the apparatus shown in Figure 8 is similar to that of the embodiment of Figure l. The inclined secondary nozzle directs the circulating pellets to one side of the bore hole so that recycled fluids and pellets tend to travel up the bore hole annulus on the opposite side of the apparatus, the pellets being carried to the region below the top or the plates 34, then travelling to the opposite side of the bore hole annulus and finally dropping downinto the top of the secondary nozzle in an orderly'manner, as shown.

The embodiments described have been presented merely by way of example and it is not intended that the invention be limited thereto. The scope of the invention is defined by the appended claims.

What is claimed is:

1. A drill bit assembly for drilling bore holes in the earth by entraining pellets in a high velocity stream of fluid comprising a first tubular member terminating at its lower end in a jet nozzle adapted to provide a downwardly directed high velocity jet of fluid, an open ended second tubular member positioned below said first tubular member in a manner aligning the inner bore of said second tubular member with said jet nozzle, the arrangement of said. tubular members being such that an upwardly directed pellet entry bpeiiing therebetvveen is provided for ent'rahce of "pellets intosaid second tubular'tneinb'ensaid opening communicating exterior of said second tubular member in the vicinity of said jet nozzle a pair of elongated plates fastened to said first tubular member and to said second tubular member and arranged in essentially parallel relation in a manner receiving between their faces a portion of said first tubular member and essentially all of said second tubular member, and a bafiie arrangement fastened to the exterior of said jet nozzle between said plates and extending above said pellet entry opening in a manner blocking off a portion of the pellet entry opening while permitting pellets to enter said opening only on one side of said second tubular member.

2. A drill bit assembly for drilling bore holes in the earth by entraining pellets in a high velocity stream of fluid comprising a first tubular member terminating at its lower end in a jet nozzle adapted to provide a downwardly directed high velocity jet of fluid, an open ended second tubular member positioned below said first tubular member in a manner essentially aligning the inner bore of said second tubular member with said jet nozzle, the arrange ment of said tubular members being such that an opening therebetween is provided for entrance of pellets into said second tubular member, a third tubular member enclosing substantially the entire length of said second tubular member and at least the lower end of said first tubular member, and a bafile arrangement interposed between said second and third tubular members and extending above the top of said second tubular member in a manner blocking off a portion of said pellet entry opening whereby pellets can enter said opening only from one side of the annular space between said third tubular member and said first and second tubular members.

3. Drill bit assembly as defined by claim 2 including an inclined bafiie member in the upper portion of the an nular space between said first and third tubular members on the opposite side of said apparatus from the accessible portion of said pellet entry opening.

4. Drill bit assembly as defined by claim 3 including at least one fluid exit opening in said third tubular member below and on the same side of said assembly as said inclined baffle member.

References Cited in the file of this patent UNITED STATES PATENTS 2,072,627 Zublin Mar. 2, 1937 2,233,260 Hawthorne Feb. 25, 1941 2,708,567 Hildebrandt May 17, 1955 

